First, Cyberdyne Systems created the computer system SkyNet to control what NORAD has done best -- nuclear weapons, stealth bomber work, and so on. The Department of Defense in the United States would be so proud of having this kind of comptuer system to do everything... However, SkyNet became self-aware in the year 1997, and decided to nuke the heck out of Russia. Russia fought back, and I guess SkyNet decided to root out humans to stop the problem of people trying to attack it. The idea of killing humans one-by-one is where the terminators came in...